Modern vehicles are generally equipped with numerous sensors, such as, for example, oil pressure, coolant temperature, transmission temperature, engine temperature, steering position, air/fuel ratio, etc. Typically, the sensors are connected to an on-board computer control module that continually monitors the sensors and regulates the vehicles functions accordingly. Generally the information generated by the sensor is continually passed along the vehicle data link as part of the vehicle diagnostic system. The vehicle diagnostic system cooperates with the factory installed gauge cluster to provide the vehicle operator with information regarding various components of the vehicle. The vehicle diagnostic system typically includes one or more separate computer control modules. Examples of such computer control modules (also known as just “modules”) are: a power train control module (PCM), an engine control module (ECM), a transmission control module (TCM), an anti-lock brake system (ABS) control module, and an air bag control module. Typically the computer control modules are connected together by a data link, forming the vehicle diagnostic system. The data link typically has a connection point, or data link connector (DLC) that is normally located under the dash of the vehicle. The vehicle diagnostic system is generally used to provide relevant information to repair technicians. The DLC provides a place to connect off-board vehicle gauges and diagnostic devices, such as scan tools and code readers, for communication with the vehicle diagnostic system.
In addition to downloading the information regarding the operation or performance of various vehicle components, the data link connectors can also be used to upload information to the various vehicle control modules. The operating parameters and/or software of the various vehicle control modules can be changed or updated. This operation is commonly referred to as “flashing” the control module. The control modules can be flashed to upgrade the performance of the vehicle, to reduce powertrain emissions, fix drivability issues, or to compensate for wear of certain components, such as engine components.